1. Technical Field
The present invention relates to a thin film type common mode filter, and more particularly, to a thin film type common mode filter in which a ferrite resin layer is formed in a spaced space between the horizontal section of the external electrode terminal and an internal electrode to decrease a parasitic capacitance component.
2. Description of the Related Art
Recently, electronic devices such as cellular phones, electric home appliances, personal computers (PCs), personal digital assistants (PDAs), liquid crystal displays (LCDs), navigations, or the like, have been digitized and accelerated. Since the electronic devices are susceptible to stimulus from the outside, a circuit is easily damaged or a signal is distorted in the case in which a small level of abnormal voltage and a high frequency noise are introduced from the outside into an internal circuit of the electronic device.
The abnormal voltage and the noise are resulted from a switching voltage generated in the circuit, a power supply noise included in a power supply voltage, unnecessary electromagnetic signal, and an electromagnetic noise, or the like, and a common mode filter (CMF) has been used as a means for preventing the abnormal voltage and the high frequency noise from being introduced to the circuit.
In general, in a differential signal transmission system, a passive component such as a diode, a varistor, or the like, has been separately used in order to suppress an electro static discharge (ESD) generated at input and output terminals together with the CMF for removing a common mode noise.
FIG. 1 is a schematic diagram showing a common mode filter structure of the related art. Referring to FIG. 1, the general common mode filter includes a base substrate 1, a first insulating layer 2 formed on the base substrate 1, an internal electrode 3 formed on the first insulating layer 2, a second insulating layer 4 formed on the first insulating layer 2 so as to receive the internal electrode 3, an external electrode terminal 5 formed on the second insulating layer 4 so as to ground an exposed end of the internal electrode 3, and a ferrite resin layer 6 formed on the second insulating layer 4.
However, in the above-mentioned common mode filter of the related art, a parasitic capacitance is generated due to structural properties.
In particular, as shown in part “A” of FIG. 1, the parasitic capacitance is intensively generated at different electrified circuits, that is, above and below a vicinity at which the internal electrode 3 and the external electrode terminal 5 are mutually close to each other, in particular, in the vicinity of a boundary therebetween.
The parasitic capacitance is a main reason that a self resonant frequency (SRF) is damaged.